According to prior art, techniques widely known and used by the industry, one or more strands, or ribbons, of reinforcing material is wound onto the mandrel, beginning at a first end thereof, in a helical configuration of one hand, and one or more successive strands, or ribbons, is wound, beginning at the second end thereof, onto the mandrel in 3 helical configuration of opposite hand. These steps are thereafter repeated with successive strands being wound adjacent to previous winding of like hand until the mandrel is completely covered, and the desired thickness is achieved. Thereafter, the member is cured.
During the winding operation there is, therefore, relative rotational as well as relative longitudinal movement between the mandrel and the winding head.
It is possible to rotate the winding head while rotating, or not rotating, the mandrel. It is also possible to rotate the mandrel while not rotating the winding head. All variations effect the desired relative rotation between the winding head and the mandrel.
Similarly, the relative longitudinal movement between the winding head and the mandrel can be effected by movement of either, or both, said members.
The concepts with respect to which the present invention is involved are not limited to adoption with any particular means for effecting relative longitudinal and/or rotational movement. As such, and purely for the sake of simplicity, the prior art and the present invention shall both hereafter be explained in terms of the situation where the winding head does not rotate but is moved longitudinally along the mandrel and the mandrel does rotate but does not itself move longitudinally.
As the mandrel is thus rotated, and the winding head is moved longitudinally therealong, the reinforcing strands engage the mandrel in longitudinally spaced relation with respect to the location of the head itself--normally in longitudinally spaced relation rearwardly of the head as the head traverses longitudinally along the mandrel. This lag in the contact of the reinforcing strands with the mandrel causes no problem until the head reverses its direction. When contact between the filaments and the mandrel does lag the location of the winding head, sudden reversal of the direction in which the winding head is moving will cause the tension in the span of the strands between the head and the mandrel to be released. As the tension of the fibers go slack, the position of the fibers about the mandrel will shift, and this adverse affect is particularly emphasized as the movement of the head immediately reciprocates past the location where the strands contact the mandrel while the strands are slackened.
Any shift in the location, and thus the orientation of the strands, creates multiple adverse affects. Not only is the reinforcing effect altered--in fact, the strands may slacken sufficiently to disengage from a portion of the mandrel and destroy the desired configuration of the article being so made--but the shift also prevents the successive layers from being accurately deposited relative to the strands already positioned about the mandrel.